Re-implanted stem cells tackle Parkinson's

A man with Parkinson's disease whose own neural stem cells were extracted from his brain, grown in the lab, and re-implanted a few months later has shown improvement in his symptoms three years after the transplant, a team of neurosurgeons announced on Monday.

The significance of the experiment is still unclear, since only one patient has undergone the procedure and a longer follow-up must be done to assess the real benefits.

But if additional transplants confirm the improvement seen in the first patient, the technique might rival, and possibly outshine, other cell-based therapies under investigation.

Doctors have long searched for cells to replace the neurons damaged in Parkinson's disease. One option is to use neural cells taken from aborted fetuses, which seem to improve the disease in some patients but have been linked to serious adverse events in clinical trials (New England Journal of Medicine vol 344, p 710).

Researchers are also testing cancer cells that can be coaxed to become neurons and there is even the possibility of using pig neurons, though they carry risks of immune rejection and transmission of unwanted viruses.

Rapid progression

Yet the best scenario of all, to use a patient's own neural stem cells to make functional neurons which can be implanted back into their brains, has remained an unattainable goal until now.

But Michel Levesque, a neurosurgeon at Cedars-Sinai Medical Center in California and vice president at Celmed BioSciences in Canada, says his team has made that scenario work in one patient. He talked about the transplant at the Annual Meeting of the American Association of Neurological Surgeons in Chicago.

The man, 57, had rapidly progressing symptoms despite treatment with drugs. Neural stem cells were extracted from his brain and the cells were grown in the laboratory for several months under conditions that favoured the development of dopaminergic neurons, the neurons that degenerate in Parkinson's disease. The new cells were then implanted into his brain, and the man was monitored over the course of three years.

"After six months of the transplantation, we observed a progressive regression of the motor deficits," says Levesque. A year later, the man's condition continued to improve, he says. After three years, he has no symptoms of the disease.

Early days

But patient's hopes should not be raised too high yet. Neurologist Arnold Kriegstein of Columbia University says more studies need to be done to really prove that the technique works.

"This is an anecdotal report, no control has been done," he says.

It is important to make sure the neurons are truly the dopaminergic kind, since other types of neurons could be very harmful if transplanted, he says: "They could create seizures."

Levesque is now planning a double-blind trial of the treatment involving 12 patients.

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